Sample injection for gas chromatographs



Dec. 8, 1970 n. JENTzscH ETAL 3,545,279

SAMPLE INJECTION FOR GAS CHROMATOGRAPHS Filed June 21, 1967 5Sheets-Sheet 1 Dec. 8, 197() D. JENTzscH ET AL V3,545,279

SAMPLE INJECTION FOR GASTCHROMATOGRAPHS Filed June 21, 1967 5Sheets-Sheet 2 Dec. 8', 1970 D, ,JENTZSCH ETALN 3,545,279

` SAMPLE INJECTION `FOR GAS `GHROlVITOCIRPI'IS Filed June 21, 1967 1 ssheets-sheet s fa, EK 52 Fig. 4"

DCC- 8, `1970 DQJENTzsc'H ETAL 3,545,279

` SAMPLE lNJECTIoNFoR GAS CHROMATOGRAPHS Filed June 21. 1967 5Sheets-Sheet L Fig'.y 5

SAMPLE `INJECTION FOR GAS CHROMATOGRAPHS Filed June'zl, 1967 5sheets-sheet 5 ///////v/////V///f/ United States Patent O 3,545,279SAMPLE INJECTION FOR GAS CHROMATOGRAPHS Dietrich Jentzsch, Uberlingen(Bodensee), Kurt Henker, Muhlhofen, Baden, and Helmut Kruger, Uberlingen(Bodensee), Germany, assiguors to Bodenseewerk Perkin-Elmer & Co.,G.m.b.H.,`Uberlingen (Bodensee), Germany, a corporation of Germany FiledJune 21, 1967, Ser. No. 647,744 Claims priority, application Germany,June 24, 1966, 1,284,660 Int. Cl. G01n 1/00 ABSTRACT F THE DISCLOSURE Asample injection apparatus for a preparative gas chromatograph includesa vessel containing a sample and having a self-sealing closure member.Carrier gas flows from a source to an inlet of the chromatograph and acoupling line, extending into the vessel, couples the vessel to theinlet. A quick acting valve for alteringcarrier gas ow is positioned inthe carrier gas line upstream from a point at which the vessel iscoupled to the inlet. Means are provided for selectively causing thecarrier gas to ilow through the coupling line to atmosphere for purgingthe line of residue sample material. Means are provided for restrictingthe ow of purging carrier gas to atmosphere thereby conserving carriergas.

This invention relates to sample injection apparatus for use with gaschromatographic instruments. The invention relates more particularly toan improvedtsarnple injection apparatus employed with preparative gaschromatographic instruments.

A preparative gas chromatographic instrument is adapted for separatingand collecting the constituents of a sample for various purposes, suchas further analysis of the constituents. Various arrangements have beenprovided for introducing the sample into a separating column foreffecting the separation. In one arrangement, pressure is established ina sample container and the sample is thereby forced into a gas streamand is carriedonto the column. In a particularly advantageous injectionarrangement which is disclosed and claimed in U.S. Pat. No. 3,365,951which is assigned to the assignee of the present invention, a throttlingmeans or iiow impedance is positioned in the carrier gas line at a pointrelatively further `upstream from an inlet of the separating column thanthe connection thereto of an enclosed vessel containing the sample. Thisthrottling means is bridged by a low flow impedance bypass line whichmay be selectively interrupted. The low impedance bypass provides forsubstantially unrestricted carrier gas flow to the chromatograph and theestablishment of the upstream pressure in the enclosed vessel. Sampleinjection is accomplished by interrupting the bypass line. A dynamicpressure drop then occurs across the throttling means and anaccompanying reduction in pressure at the inlet of the separating columnoccurs. The pressure previously established in the supply vessel thenforces a sample onto the separating column. It is an object of thisinvention to provide an improved form of injection apparatus of the typereferred to.

The form of sample injection apparatus described is adapted for therepeated introduction of a one and the same sample substance primarilyfor preparative purposes. When the sample vessel is removed such as whenthe` sample substances are being replaced or substituted, a relativelystrong carrier gas stream discharges through the connection line,thereby leading to an undesired loss 3,545,279 Patented Dec. 8, 1970 ACCof carrier gas. It is desirable to limit this discharge of carrier gasto a certain extent, maintaining at the same time the necessaryscavenging function.

It is another object of the present invention to provide an injectionapparatus of the type decribed which is particularly suitable for theinjection of diierent sample substances.

A further object of this invention is the provision of an injectionapparatus of the type described. which is adapted for injecting samplesof differing substances while substantially reducingthe possibility ofcontamination.

In accordance with a feature of the present invention, a carrier gas issupplied to a chromatograph through a carrier gas line.` An enclosedvesselcontaining a sample to be injected is coupled to the carrier gasline by a relatively narrow conduit. Valving means are provided in thecarrier gas line upstream from a point of sample introduction foraltering the carrier gas flow rate. The

sample vessel includes self sealing means for providing a gas seal andthrough which the relatively narrow conduit may be introduced andwithdrawn for substituting sample j substances. Means are alsoprovidedfor purging sample ilow paths upon withdrawal of the narrowconduit from the vessel.

In a particularly advantageous scavening arrangement, a connection linefor coupling the vessel to the gas ilow stream extends longitudinallythrough a piston about which is moveably positioned a cylinder having athrottling outlet. Means provide a gas seal between the cylinder andpiston and the cylinder is provided with a selfsealing means on one facethereof. Means bias the piston and the cylinder respectively in a mannerfor maintaining the connection line with the cylinder.

In this particular scavening arrangement, as the sample is injected, theend of the capillary connection line is positioned internally of thecylinder :and the carrier gas is throttled to the atmosphere through athrottling outlet. When sample introduction is desired, a samplecontainer having a self-sealing diaphragm is forced against the cylinderand forces the cylinder longitudinally against the action of the biasingmeans. In doing so, the capillary pierces the cylinder diaphragm, exitsfrom the cylinder, and pierces the diaphragm of the sample vessel. Thepressure will now build up in the sample vessel and when the carrierstream is interrupted, a quantity of the sample is forced from thevessel and onto the column. When carrier gas flow is re-established, thesample vessel is withautomatically moves over the capillary and enclosesthe sameas the capillary is drawn within the cylinder through theself-sealingi diaphragm. Thus, carrier gas flows to atmosphere through aiiow restrictive means.

In sample injectors of the type for injecting liquid samples, it is alsoadvantageous to utilize heatable connecting lines for heating thecouplinglines between the injection of different samples for thepurposes of scavening and cleaning.

These and other objects and features of the present invention lwillbecome apparent with reference to the following specifications anddrawings wherein:

FIG. l is a diagram of an apparatus constructed in accordance with thefeatures of the present invention;

FIG. 2 is a diagram of a portion of the apparatus of FIG. 1 illustratingan alternative arrangement for injecting and scavenging;

IFIG. 3 illustrates a scavenging arrangement for use in the alternativearrangement of FIG. 2 and which limits the loss of carrier gas duringthe interval between sample insertions;

FIG. 4 illustrates an alternative injection and scavengof FIG. 2; and, i

FIGS. 5 and 6 illustrate the apparatus of FIG. 4 in different positionsduring the injection and scavenging modes.

In the embodied form according to FIG. 1 the carrier gas flows from asource 8 through a pressure-reducing valve 10, a filter l12., aprecision pressure regulator 14 and a quick-acting gate valve 16. Valve16 which comprises a magnet valve (i.e., solenoid actuated) is coupledto the inlet 18 of a gas chromatographic separating column. A sample tobe injected is contained in a sample vessel 20 which is sealed at thetop thereof by a selfsealing diaphragm 22. A relatively narrow conduitcomprising a capillary connection line leads oif from the inlet 18 ofthe separating column, and which, in FIG. 1 includes two members. Thefirst member 24 is coupled between the inlet 18 and change-over cockvalve 26 and the second member 27 is coupled to the changeover cock 26and terminates in a cannula 28. A line 32 including a throttle 34branches off from the carrier gas line 30 and is coupled to thechange-over cock 26. A fourth line 36 is also coupled to the change-overcock 26 and leads to the atmosphere via a ow restricting throttle 38.The cock valve 26 is formed with two opposing grooves 40 and 42extending across an angle of about 90. In one setting thereof line 24 isconnected with line 36 via groove 40 and line 32 is connected withcannula 28 via groove 42 as shown in FIG. 1 during a scavenging mode ofoperation. In the other setting of the changeover cock an injection modeof operation is established and groove 42 connects line 24 with thecannula 28 and groove 40 connects line 32 with line 36.

The operation of the sample injector of FIG. 1 can be described asfollows. Initially, the magnet valve 16 is opened and carrier gas willflow through line 30 to the inlet 18. The line 24 is connected with thethrottled outlet line 36 via groove 40 of the change-over valve 26. Thethrottled line 32 is coupled to the exposed cannula 28 via the groove42. Carrier gas ows to the atmosphere through both of these paths. Thisliow which is restricted by throttles 34 and 38 thereby cleans theconnection line 24, 28 and the grooves 40, 42 from residues of thesample substance from the preceding sample injection.

The cannula 28 is then passed through the self-sealing diaphragm 22 ofthe sample vessel 20. It is possible to inject a gaseous or vaporoussample. When a liquid sample is injected, the cannula is positionedbeneath the surface level of the liquid sample. Finally, the sample mayalso be taken from the saturated atmosphere above a sample liquid.

As soon as the cannula 28 has pierced the diaphragm 22, the cock 26 ischanged over. IGroove 42 no'w connects the sample with the inlet 18 ofthe separating column via the cannula 28, line 27, and line 24. Thecannula 28, line 27, and line 24 comprise a connection line between thevessel 20 and column inlet 18. Since the magnet valve 16 is still open,the full carrier gas pressure becomes effective at the inlet 18 of theseparating column. The carrier gas also enters into the sample vessel 20'via the connection line 24, 27 and 28 so that a pressure is built up inthe vessel.

Sample injection is subsequently achieved by closing the magnet valve1-6. The pressure at the inlet 18 of the separating column therebydecreases, since inlet 18 is coupled to the atmosphere via theseparating column. A sample substance is then forced by virtue of thispressure dilerential from the sample vessel 20 to the column via theconnection line 24, 27 and 28.

In the scavenging mode, the magnet valve 16 is opened. The Ifull carriergas pressure is again established at the inlet 18 of the separatingcolumn and the sample injection is interrupted. The valve 26 is changedover. A connection is now established via groove 40 between line 24 andthe throttled outlet line 36 through which a carrier gas stream flowsinto the atmosphere. A carrier gas liows from the branch line 32 to thesample vessel 20 via groove 42, line 27, and cannula 28. The vessel 20is now withdrawn so that this carrier gas stream also discharges intothe atmosphere. These carrier gas streams are effective to scavenge theline portions 24, 27, and 28 which have come into contact with samplesubstance and the grooves and 42 of the change-over valve. The sampleinjector is now ready yfor a new sample injection with another samplesubstance.

FIG. 2 illustrates an alternative embodiment of the invention duringsample injection. The arrangement is similar to that of FIG. 1. However,the change-over cock 26 is omitted. The cannula 41 which hereincomprises the connecting line leads directly to the inlet 18 of theseparating column and is mounted at at 42. The cannula 4.1 is piercedthrough the diaphragm 22. When the magnet valve 16 is open and the fullcarrier gas pressure is present at the inlet 18 of the separatingcolumn, this pressure is transmitted to vessel 20 via cannula 41. Asvalve |16 is shut olf, the pressure at the inlet of the separatingcolumn decreases and sample substance is dralwn into the column inletfrom vessel 20. This dosing action is stopped when valve 16 opens again.When the sample vessel 20 is Withdrawn from cannula 40, a strong carriergas stream discharges through the cannula, Which effects cleaningthereof from residues of the sample substance.

Generally, this strong scavenging carrier gas stream would in the longrun lead to an intolerable loss of carrier gas. For this reason inaccordance 'with FIG. 3 there is provided a scavenging vessel 44 with aself-sealing diaphragm 46 and an outlet throttle 48. The cannula 40 ispierced through diaphragm 46 so that it terminates now in the scavengingvessel 44. Now only a carrier gas stream defined by throttle 48 candischarge.

The embodied form of the invention as illustrated in FIGS. 4, 5, and 6is based on a similar principle. There too, the basic design is similarto that of FIG. 1 and FIGS. 2 and 3, respectively. The cannula 50comprising the coupling line is centrally guided longitudinally througha piston 52. The piston 52 has sliding thereon a cylinder '54 and a gastight seal is provided there between by means of an O-ring 56. Thecylinder 54 is formed With a central aperture 58 in the lower facethereof. This aperture 58 is closed off by a self-sealing silicon rubberdiaphragm 60. Diaphragm `60 is held by a cap 62 which is screwed ontothe end of cylinder 54 and is formed with an aperture k64 in alignmentwith aperture '58. A screw cap 166 is screwed on at the upper end of thecylinder, which with the inner flange thereof abuts a shoulder 68 ofpiston 52 in a position of rest (FIG. 5) and limits the movement ofcylinder 54 upwardly. A bias spring 70 forces cylinder 54 upwardly asillustrate din FIG. 5. In the position of FIG. 5, the end of the cannulal50 is located internally of cylinder 54, in alignment with theapertures 58 and 64. 'Ihe interior of cylinder 54 is communicated withthe atmosphere via an aperture 71 and a throttling capillary tube 72which is helically wound about cylinder 54.

The arrangement of FIGS. 4, 5, and 6 operates as follows:

In the normal state the sample injector is in the position illustratedby FIG. 5. A carrier gas stream enters into the interior of cylinder 54through cannula 50, is throttled via the capillary throttle 72, andflows to atmosphere. For sample injection, (FIG. 4) the sample vessel 20is forced against cylinder 54 from below with the self-sealing diaphram22 thereof and moves the same upwardly against the action of spring 70.In so doing, the cannula 50 passes through opening 58, pierces throughthe self-sealing diaphragm 60, passes through opening 64 and piercesthrough diaphragm 22 so as to protrude into the sample vessel with theend thereof. When the magnet valve 16 shuts olf now, as is shown in FIG.4, sample substance is drawn into inlet 18 in the manned describedhereinbefore until valve 16 opens again. Upon withdrawal of the samplevessel 20, cylinder 54 automatically moves again over the end of cannula50 so that the carrier gas can discharge only ina throttled flow in themanner as described. It it is desired to have a stronger carrier gasstream temporarily for intensively scavenging cannula 50, cylinder 54may be forced back so that the end of cannula 50 protrudes throughdiaphragm 60, as is illustrated in FIG. 6, and exhausts to theatmosphere.

The arrangement as hereinbefore described is a relatively simple andadvantageous arrangement for handling and scavenging. It facilitates aquick and simple replacement of the silicon rubber diaphragm 60.

For sample injectors forliquid samples that is provided a heating bymeans of which the connection line is heatable up to a temperature abovethe temperature at which the least volatile sample componentvaporizes.By such a heating between the individual sample injections in connectionwith the scavenging streams, the sample residues are removed from thesystem. Thereafter the connection line may again be cooled down to itsoperating temperature, such as by means of a blower.

While a particular arrangement of the present invention have beendescribed, various moditications may be made to the apparatus by thoseskilled in the art without departing from the spirit of the invention.

What is claimed is:

1. Sample injection apparatus for a gas chromatograph having aseparating column, said injection apparatus comprising:

an enclosed vessel containing a sample;

a quick-acting valve means having first and second selectable stableconditions;

iirst conduit means defining a first carrier gas passageway forconveying a carrier gas between a gas source and the inlet of saidseparating column through said valve means, the second condition of saidvalve means providing a flow impedance in said 'first passageway;

second conduit means deiining a second gas passageway between saidsample vessel and said column inlet, said second conduit means havingone end thereof coupled to said column inlet; means for selectivelycommunicating the other end of said second conduit means with theinterior of said sample vessel for establishing a pressure in saidvessel when said Valve means exist in said first condition, and a iiowpath for said sample between said vessel and said inlet when said valvemeans exists in said second condition, whereby said sample is caused toflow over said flow path by the pressure established in said vessel;and,

scavenging means for passing carrier gas through said second conduitmeans and exhaust to atmosphere when said other end of the secondconduit is withdrawn from communication with the interior of said samplevessel, thereby cleansing said second conduit means of residue sample.

2. The apparatus of claim 1 where said means for selectivelycommunicating includes a self-sealing diaphragm defining a wall portionof said sample vessel and said other end of the second conduit means isadapted for extending through said diaphragm into said vessel.

3. 'I'he apparatus of claim '1 wherein `said scavenging means includesmeans restricting the flow of carrier gas to atmosphere.

4. The apparatus of claim 1 wherein said second conduit menas includes afirst member coupled to said column inlet and a second memberselectively communicable with the interior of said sample vessel, andsaid scavenging means simultaneously passes carrier gas through a lirstgas flow path exhausting to atmosphere which includes said first member,and, through a second gas ow path exhausting to atmosphere whichincludes said second member.

5. The apparatus of claim 4 wherein said scavenging means includes avalve body having first, second, third, and fourth ports and means forproviding gas iiow passageways between said rst and second ports andbetween said third and fourth ports during a scavenging mode ofoperation, and, gas dow passageways between said rst and fourth portsand Ebetween said second and third ports during a sample injection modeof operation,

means including a iiow restrictor for conveying a carrier gas from asource thereof to said third port, means including a flow restrictor forcoupling said second port to atmosphere, and,

said irst` member is coupled to said first port, and

said second member is coupled to said fourth port.

6. The apparatus of claim 1 wherein said scavenging means includes anenclosure having an aperture;

a conduit penetrable self-sealing body positioned at said aperture, and,

said other end of the second conduit means selectively terminatingwithin said enclosure or extending through the self-sealing body of saidenclosure.

7. The apparatus of claim 6 wherein flow-restrictive means are coupledto said enclosure for exhausting said enclosure to atmosphere.

8. The apparatus of claim 7 wherein said enclosure includes a cylinderbody with said aperture formed therein at one end thereof;

a piston body positioned coaxially within said cylinder;

said cylinder reciprocating motion with respect to said piston;

said second conduit means extending longitudinally through said pistonwith said other end thereof extending from said piston in alignment withsaid cylinder aperture; and, means biasing said piston away from saidcylinder aperture.

References Cited UNITED STATES PATENTS 2,120,248 6/ 1938 Hinchman 222-52,496,258 2/ 1950 Alexander 222--83X 2,959,677 11/ 1960 Robinson et al73-23.1X 2,593,552 4/ 1952 Folkman 222-5 3,238,784 3/ 1966 Dorsey 73-4253,364,958 1/ 1968 Sartor 141--329X 3,383,923 5/ 1968 Conche ---s 73-421FOREIGN PATIENTS 1,025,510 4/ 1966 Great Britain 73-23.1

`CHARLES A. RUBI-IL, Primary Examiner

